1. Field of the Invention
The present invention relates to a fan control apparatus, and more particularly to a fan control apparatus that controls a fan that is rotary driven by being supplied with a fluid and serves to generate a propulsion force of a flying object.
2. Related Background Art
A propulsion force for causing a VTOL (Vertical Take-off and Landing) apparatus to fly has conventionally been obtained by supplying the air by an bleed gas turbine engine and rotary driving a fan. For example, Japanese Patent Application Laid-open No. 2007-22268 discloses a VTOL apparatus comprising two gas turbine engines and two air bleed channels and the apparatus flies by driving a fan with compressed air discharged from the air bleed channel.
However, in such a VTOL apparatus having two engines and two air bleed systems, an abnormality sometimes occurs in one air bleed system or one of the engines sometimes fails and the so-called OEI (One Engine Inoperative) state is assumed. In the case of such OEI, the revolution speed of the normally operating engine and the turbine inlet temperature are increased over those of the rated output to compensate the insufficient fan drive power. However, immediately after one engine fails, the revolution speed of the normally operating engine is low. As a result, when the required output abruptly increases, a surge or the like occurs, the engine is overloaded, and there is a risk that even the engine that has not failed will not be able to operate normally.
Further, when an abnormality occurs, as described above, in one air bleed system, the required amount of air has to be compensated by the normally operating system, but where the required amount of air is compensated by the normally operating system alone, a certain time is needed to enable the supply of a necessary amount of air. Therefore, such an approach is not suitable for flying objects that require a short response time, such as VTOL apparatuses.